I don't know where they come up with this stuff, to tell the truth. Everyone that shoots fingers has a different release, some rougher and some smoother. To say every fingers shooter has to add exactly 9 pounds to his draw weight to get the right spine is, in my opinion, absolutely ridiculous.

The only real way of knowing what spine you need is to try the arrows.

The only info I could find on The Boss arrows was that a 32" shaft is good from 55-70 lbs, and that was just general BS advertising copy. I have grave doubts it was accurate. Same exact wording on two different general outdoors products sites that specialize in clearance items.

With that 55-70 lb spread, kinda sounds like they might be made by GoldTip (?) so I'd look at 5570's on GoldTip's chart to get a better idea of what they can handle.

General rule of thumb though, for every inch you shorten the arrow, you've stiffened it by 5 pounds in spine.